1. Field of the Invention
The present invention relates to a process for industrially producing .alpha.-hydroxyisobutyramide by the hydration reaction of acetone cyanohydrin. .alpha.-Hydroxyisobutyramide is an industrially useful substance which serves as an intermediate starting material for methacrylamide and methyl methacrylate.
2. Description of the Related Arts
It is publicly known that manganese dioxide is used as a solid catalyst in the hydration reaction of acetone cyanohydrin. According to any of the conventional processes, .alpha.-hydroxyisobutyramide is obtained by the reaction of acetone cyanohydrin with water as shown by the following reaction equation at a temperature of 40.degree. to 100.degree. C. in the presence of manganese-based catalyst and preferably an acetone-based solvent in a yield of 60 to 95%. EQU CH.sub.3 C(CH.sub.3)(OH)CN+H.sub.2 O.fwdarw.CH.sub.3 C(CH.sub.3)(OH)CONH.sub.2
However, the actual result of the hydration reaction thereof by the use of the publicly known manganese-based catalyst involves serious problems from the viewpoint of stable operation in an industrial scale due to the disadvantages that the product .alpha.-hydroxyisobutyramide is obtained in low yield with unsatisfactory reaction achievement and catalyst activity deteriorates with the elapse of time even in the case of high performance in the initial stage of the reaction, thereby lowering the yield of the product. The present inventors have already found that the catalyst comprising, as the essential component, manganese dioxide prepared under specific conditions (hereinafter referred to as "modified manganese catalyst") is effective and such catalyst has been disclosed in Japanese Patent Application Laid-Open No.93761/1991. Although the modified manganese catalyst prepared under the specific conditions has an extremely high activity and a long service life, it has been proved that the use thereof as a fixed-bed catalyst in a solid-liquid contact reaction process causes a white crystal to deposit at the inlet and on the downstream side of the catalyst packing section from the start of the reaction to the relatively initial stage thereof depending upon the reaction condition, thus raising the trouble of clogging the catalyst bed.